The present invention relates to apparatus for attachment to a rotary power mower for collecting the grass clippings cut thereby. In particular, this invention relates to grass collection apparatus for use with tractor-mounted or riding-type rotary mowers.
In such rotary mowing machines, the action of the blades serves to create a vacuum within the blade housing and generates a stream of air which is directed through an exhaust outlet to a collection container, the cut grass clippings being entrained in this airstream for delivery to the collection container. A major problem with such devices is the creation of substantial back pressure within the collection container. This back pressure tends to inhibit the flow of air and entrained clippings into the collection container, leading to clogging of the conduit means and, ultimately, the blade housing, and severely decreasing the vacuum created in the blade housing. This vacuum is essential for pulling the grass into an erect position for proper mowing action, and for sucking the grass clippings up into the blade housing and through the exhaust opening. Thus, a loss of vacuum both impairs mowing efficiency and serves to permit heavier clippings to fall back onto the lawn, thereby seriously interfering with the vacuum-cleaning action of the mower. The decreased airflow resulting from the loss of vacuum also fosters the buildup of scale on the blade housing and associated conduits.
Prior art grass collection systems for mowing machines have attempted to overcome this back pressure problem by several methods. Some such devices have utilized auxiliary blowers for maintaining negative pressure within the collection container. But this arrangement obviously entails considerable additional expense and complexity, and decreases the tractor power otherwise available for propelling the tractor and the mowing blade.
Other systems have utilized a collection container which is wholly or partially porous or of mesh-like construction so as to readily permit the escape of air therefrom. But even in such porous containers, the grass clippings will tend to quickly line the inside of the container walls, closing the openings therein and creating in effect a sealed closed container, whereupon back pressure rapidly builds up.